In the swirl that is the Super Bowl, there are predictions of passes and runs, of what will happen and why. Predictions made with certainty and volume.

But the future of the game and those who play it is every bit as hard to predict because of concerns raised about the effect that football is having on players. President Barack Obama said recently that if he had a son, he would have to "think long and hard" about letting him play football.

"Certainly it's a dangerous game and we're finding out more and more, every day, the long-term effects that this game can have," said Baltimore Ravens center Matt Birk, a 15-year NFL veteran. "But there is a lot we all don't know yet."

More than 4,000 former NFL players have sued the league, charging that teams, their medical staffs and the league have failed to do enough in diagnosing concussions, or done enough in alerting players to the risks. Junior Seau's suicide last May — the former linebacker shot himself in the chest — pushed the issue of the post-career lives of NFL players to the forefront.

Concerns over the effects of concussions, both those formally diagnosed and those that were not, have grown. Researchers at the National Institutes of Health announced recently that Seau suffered from chronic traumatic encephalopathy (CTE), a brain disease linked to repeated impacts to the head from playing football. Seau never was publicly diagnosed with a concussion during his NFL career.

CTE also has been linked to the suicide of former Chicago Bears safety Dave Duerson.

Symptoms such as memory loss and depression have been cited in former players who had the disease, but the only way to diagnose CTE is with an examination of the brain tissue at autopsy.